This includes a fix for builds on Windows using mingw.
See protocolbuffers/protobuf#8286

- Adds windows to the bindist pipeline os-matrix.
- Specify bash as the shell for the pipeline actions.
  (Default on Windows would be powershell)
- Extend start script to support Windows.
- Add CI tag filters to disable unsupported tests on Windows.
- A `sh_test`s name must have an extension matching that of `srcs`.
  ```
  ERROR: D:/a/rules_haskell/rules_haskell/tests/BUILD.bazel:134:8: in sh_test rule //tests:test-binary-with-data: Source file is a Windows executable file, target name extension should match source file extension
  ```
- Use `rule_test_exe` instead of `rule_test` where appropriate.
- Disable stack_snapshot lock files on Windows
  They were pinned on Linux and contain platform specific dependencies, e.g. `unix`.
- Update protobuf to 3.15.1
  This includes a fix for builds on Windows using mingw.
  See protocolbuffers/protobuf#8286
- Skip c2hs tests on Windows
- Disable tests requiring nm
  `nm` is not in default `PATH` in Windows. We could obtain it either via
  `$(NM)` make variable or directl from the `CcToolchainInfo`.
- Skip solib test on Windows
- Skip runfiles-tree test on Windows
- Disable haddock tests on Windows
  The haddock wrapper needs to be converted to a `sh_binary`.
- Skip cabal library test on Windows
  Bazel builds are not sandboxed on Windows. These tests fail because
  both Cabal files are visible in the same build actions.
- Remove libz.dll.a in GHC bindist, similar to other .dll.a libs.
- Disable haskell_import test on Windows
- Skip test on Windows that needs rlocation
  These can be fixed later on by using rlocation instead of expecting
  files to be available under a hard-coded relative path.
- Skip proto test on Windows